1. Field of the Invention                The invention related generally to the manufacture of thin film polyimides. More specifically, the invention relates to a method of thermal seaming sheets of a polyimide material.        
2. Background Art
Thin film polyimides are commonly used on satellites and other space flight equipment. They are typically thin polymer films with an applied reflective metallized evaporative coating. These films are used as solar shields, solar concentrators, solar sails, etc. A reflective membrane may be used to protect orbital structures and equipment such as satellites from direct exposure to solar radiant flux. Alternatively, a reflective membrane may be used to concentrate solar energy on equipment such as a solar panel that powers a satellite.
Sheets of film are often seamed together to make a larger thin film sheet. However, the films are usually 2 mils thick or less and the material used is sensitive to mechanical tears and contamination. Welding had not traditionally been used because polyimides and other similar polymeric materials do not possess a definite established melting point. The materials also decompose rapidly if heated to their melting point which makes conventional welding techniques impractical.
Prior art techniques of seaming include bonding the materials with am adhesive or alternatively employing a mechanical fastener. However, adhesive seaming is messy and prone to contamination. Additionally, adhesives such as acrylic or silicon lose mechanical strength at low temperatures. A mechanical fastener, such as stitching with thread, is prone to tearing especially if single layers of materials are seamed together. Consequently, a method for effectively seaming thin film polyimides is needed.